The study of protein phosphorylation is expected to enhance our understanding of biochemical events linking the neurotransmitter receptor to the physiological responses it elicits. During the past year we have extended our research on a unique brain phosphoprotein we had described previously, whose phosphorylation is inhibited by S-100 and by calmodulin. This protein, called S100 modulated phosphoprotein (SMP), is found to be present in both brain supernatant and membranes. The membrane SMP was indistinguishable from the supernatant SMP. A brain-extracted growth factor called neurite elongating factor (NEF) was found apparently to convert SMP from the 87k molecular weight form to a 90k form. This property of NEF was further characterized. Evidence was obtained to suggest that some hormone receptor sensitivity may be regulated by a mechanism involving protein phosphorylation by C-Kinase. Further elucidation of this process is in progress. Our previous observation regarding the changes of protein phosphorylation associated with kindling were extended. Three phosphoproteins were identified of which the phosphorylation was found to be consistently enhanced in amygdala kindled animals. Such a change in protein phosphorylation was found to be localized to amygdala and could not be detected in prekindled animals.